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Re: Decomposing a bit field? [message #71811 is a reply to message #71716]

Wed, 21 July 2010 03:29

Steve[5]
Messages: 10
Registered: September 2007

Junior Member

Rob wrote:

> for i=0, 31 do begin test[i]=(ISHFT((15982561),-i) AND 1B)
>
> However, for example bits 1-4 need to be combined (and contain data
> from 0-15). As I don't quite understand what the code above is doing
> I'm not sure how to (or if it can be) modified to not just operate on
> the individual bits but on groups of bits.

ISHFT - moves bits right or left so that the bits you want are at the
end of the value. AND selects the bits that you want.
>
> What I need to extract is the information in the folowing form:
>
> Bit 0: 0 or 1

bit0= ishft(15982561,0) and 1B
> Bits 1-4: 0-15

bits1to4 = ishft(15982561,-1) and 17B

> Bit 5: 0 or 1

bit5 = ishft(15982561,-5) and 1B

> Bits 6-8: 0-8

bits6to8 = ishft(15982561,-6) and 7B

> etc
>
> Thanks in advance

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[Message index]

		Decomposing a bit field? By: rjp23 on Wed, 21 July 2010 02:40
		Re: Decomposing a bit field? By: Chris[6] on Wed, 21 July 2010 15:41
		Re: Decomposing a bit field? By: penteado on Wed, 21 July 2010 09:21
		Re: Decomposing a bit field? By: David Fanning on Wed, 21 July 2010 09:09
		Re: Decomposing a bit field? By: Steve[5] on Wed, 21 July 2010 09:04
		Re: Decomposing a bit field? By: rjp23 on Wed, 21 July 2010 04:25
		Re: Decomposing a bit field? By: Chris[6] on Wed, 21 July 2010 03:33
		Re: Decomposing a bit field? By: greg.addr on Wed, 21 July 2010 03:31
		Re: Decomposing a bit field? By: Steve[5] on Wed, 21 July 2010 03:29

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